The following references are believed to represent the state of the art:
US Published Patent Application 2003/0037333 Ghashghai, et al.;
US Published Patent Application 2004/0019675 of Hebeler, J. R. et al.;
US Published Patent Application 2005/0120366 of Thurbon;
US Published Patent Application 2005/0229199 of Yabe;
US Published Patent Application 2007/0288627 of Abella, et al.;
US Published Patent Application 2008/0162200 of O'Sullivan, et al.;
US Published Patent Application 2009/0052859 of Greenberger;
U.S. Pat. No. 4,769,697 to Gilley, et al.;
U.S. Pat. No. 5,771,307 to Lu, et al.;
U.S. Pat. No. 5,892,856 to Cooper, et al.;
U.S. Pat. No. 5,913,067 to Klein;
U.S. Pat. No. 6,400,996 to Hoffberg, et al.;
European Published Patent Application EP 1,318,679 of Thomson Licensing S.A.; and
PCT Published Patent Application WO 2007/114789 of Heulab PTE Ltd.